The phrase "a simple certain" is not correct and does not convey a clear meaning in written English.
It seems to be an attempt to describe something that is straightforward and definite, but the combination of "simple" and "certain" does not work together in this way.
Example: "There is a simple certainty in the way she explained the process."
Alternatives: "a clear certainty" or "a straightforward certainty".
This is hardly alien to our understanding of how the body, mind and external circumstances work inextricibly together, and how difficult it is to discern any single cause of mental functioning, positive or negative, no matter how much we yearn for a simple, certain explanation.
Some of the phenomena we observed were expected, while others, such as the tendency of many evolving organisms to become very complex and to accumulate a large number of non-essential genes, did not yet receive a simple, certain explanation.
Even though most deeds are relatively simple, certain elements can have a significant impact on how the new owners hold title.
A simple and certain rule can influence behaviour with a degree of certainty (but it will sometimes make us drive more slowly than we need to, or let us drive more quickly than we ought to).
Founded in 1998, StarMine has built its business on a simple premise: Certain analysts are more worth listening to.
Since 1998, StarMine has built its business on a simple premise: Certain analysts are worth listening to more than others.
Since 1998, StarMine has built a business on a simple premise: Certain brokerage analysts are worth listening to more than others.
In the aftermath of the 9/11 attacks, New Yorkers were horrified by the fact that the simple, certain form of their skyline had been altered.
If you're concerned that your rounding shoulders are more than just a simple slouching issue (certain physical conditions such as scoliosis or kyphosis may require professional correction) or if they're causing you pain, it may be a good idea to see your primary health care provider to get a physical therapy referral.
Advocates for one side or the other do not tend to see their bias as a simple prejudice to certain types of information over others – instead, it's a matter of morality.
Yet there is a simple truth that certain diseases become much more common as industrialization occurs in societies.
